Authors
A K Chambers3; N D Sargison4; F Kenyon2; D H Nussey1; 1 Ashworth Laboratories (University of Edinburgh); 2 Moredun; 3 Roslin Institute (University of Edinburgh); 4 Royal (Dick) School of Veterinary Studies (University of Edinburgh) Discussion
Parasitic helminths present significant welfare and economic costs to the small ruminant industry. Multi-parasite co-infection is common, but the differences in species-composition between-hosts and within-hosts are not well understood. Different helminth species vary in pathogenicity and sensitivity to anthelmintics, and the impact of production strategies on the nematode infra-community structure is unknown. The unmanaged Soay sheep on St Kilda provides an ideal study population. Longitudinal differences in parasitic burden were established by faecal egg counts (FEC), which corresponded with the sheep’s dynamic life-history. However, FEC is not suggestive of true parasite counts, and species- structure is unknown. PCR-based methods to identify 3rd-stage nematode larvae offer a non-invasive method of parasite assessment. Utilising real-time PCR methods (AusDiagnostics), host sex/age differences in major production-limiting nematodes have been identified. However, this technique is restricted by primer availability for potentially novel species. High-throughput barcoding of the nematode ITS-2 rDNA locus provides a rapid method of biodiversity assessment, utilising nematode-specific universal primers. This technique has been found to accurately quantify gastrointestinal nematode communities in cattle, and would offer greater sensitivity in future assessments. Understanding the complexities of an untreated parasite community could inform future control methods. 
